PA2906-Coastal Hazard Assessment-R3 · MCU21/0212

                                                 Internal use only




induced erosion predicted by Vellinga (1983). The Department provides the following recommendation in
relation to defining a storm event:

          “For a tide-dominated coast where storm tide levels can be large, the parameters
          adopted for the minimum design storm are:
                storm tide level corresponding to an average recurrence interval of 1-in-
                 100 years
                wave height for a moderate storm using the 1-in-20-year significant wave
                 height (Hs).

          However, for wave-dominated coastlines where extreme storm tide levels can be
          relatively minor, such as the Gold Coast, the significant wave height and duration
          of the storm event are major factors influencing short term erosion, rather than
          storm tide. Hence it may be necessary to consider a larger wave event (for
          example, a storm event with a 1-in-100 ARI) and a moderate storm tide level.
          Decisions on appropriate parameters to be used must be based on local
          conditions and the experience of the coastal engineer undertaking the
          assessment.”




Figure 17 Sketch of pre-storm and predicted post-storm profiles based on Vellinga (1983)


In relation to the probability of such an event occurring the Department of Environment and Heritage
protection (2013) states:

        “Although the abovementioned probability of occurrence may appear to be fairly
        high, it is considered that this choice is reasonable when considered in
        conjunction with the method used to determine erosion prone area widths. This
        method implies that the erosion prone area has sufficient width to accommodate
        the design storm erosion in 100 years’ time, when all of the estimated long-term
        erosion has occurred. Therefore, it also follows that for much of the 100-year
        planning period, the erosion prone area is sufficient to accommodate a larger
        storm than the one selected for design purposes. In fact, in the most critical last

03 June 2022          66 SEAVIEW TERRACE, SUNSHINE BEACH                          PA2906-RHD-ZZ-XX-RP-Z-0001   25